Covid-19: Discussion about isolation time after corona infection

Breaking chains of infection – this is the most important measure in the fight against the pandemic. It is particularly crucial that there are as few contacts as possible in which the Sars-CoV-2 virus can be passed on from an infected person to a person who has not yet been infected. A new meta-study from Great Britain now suggests that infected people may have to stay at home shorter than before – and the spread of the virus could still be prevented.

In the debate, however, it is first important to distinguish between two terms: quarantine and isolation.

• quarantine means the separation of symptom-free contact persons who have been proven to be infected. It can either be voluntary or ordered by the authorities. The quarantine period in Germany will be shortened from 14 to 10 days on December 1st – on condition that a negative corona test, regardless of whether it is a PCR or a rapid antigen test, is available at the end of this period. “10 days of quarantine with a quick test at the end is just as safe as 14 days of quarantine without a test,” said Federal Health Minister Jens Spahn. “But it means four days fewer restrictions for those affected.”

• From Isolation one speaks against it, if it is proven that infected people are not allowed to leave their apartment in order not to infect anyone. The time frame for this has been ten days so far, at least if the patient has been symptom-free for 48 hours at the end of this time and – if the course is severe – can also present a negative PCR test.

How long quarantine or isolation should last depends on the answer to a crucial question: How long does an infected person shed such large amounts of virus that they can infect other people? From an epidemiological point of view, in case of doubt, it makes sense to choose the longest possible period. However, there is a risk that people may not follow the rules. Anyone who takes to the streets before the deadline expires can be a danger to others there. Ultimately, the official rules can at best be checked selectively.

In Germany, at the end of the summer, there were lively discussions about shortening quarantine and isolation times. This shortening has now also been decided on in the quarantine. From their point of view, the new meta-evaluation by the British researchers now suggests talking again about the length of the isolation. The team around Mücke Çevik from the University of St Andrews reports in the specialist magazine “The Lancet Microbe” on findings on the question of when and how long infected people shed the Sars-CoV-2 virus.

Short transmission window

The researchers looked at 79 studies on Sars-CoV-2 and 19 other studies on related pathogens. “In none of the studies was a live virus detected after the 9th day of illness despite persistently high viral load,” they concluded. Viral loads in the upper respiratory tract seem to peak in the first week of illness. Symptom-free infected people also seem to have about the same amount of virus in them as patients with symptoms. In asymptomatic people, however, the virus apparently disappears from the body more quickly.

“This meta-analysis shows how short the transmission window is,” says virologist Michael Mina from Harvard University, who was not involved in the study. Even those who do the PCR test at the earliest possible point in time have already secreted 90 percent of the viruses by the time they get the result.

People with Covid-19 are usually most infectious a day or two before symptoms appear, the study said, and until about five days after they start. Nevertheless, in some cases, patients can carry genetic fragments of the pathogen in the nasopharynx for up to three months.

RKI experts see shortening as critical

In the case of those who are actually infected, the incubation period and infectivity are better to limit than for contact persons. Therefore, a shortening of the isolation period can also be discussed here with better facts. A period of just five days could cause more infected people to actually adhere to the isolation, Çevik said. Their reasoning is likely to be based on an opinion poll from August, according to which only 20 percent of respondents in Great Britain actually follow the rules of self-isolation. Reasons for this could be economic in nature – or the feeling that you are no longer sick.

At the end of September, a research group at the Robert Koch Institute presented an opinion on the duration of quarantine and isolation for Covid-19. “Shortening the isolation period to less than 10 days would […] go hand in hand with a correspondingly large increase in risk, «it says.